Carburetor



' Nov. 27, 1934. A. M PRENTISS CARBURETOR Filed Jan. 5, 1931 INVENTOHR. la upfin M premllss ZJW 7 MM]:

ATTORNEY Patented Nov. 27, i934 UNETED} STATES PATENT OFFECE CARBURETOR Illinois Application January 5, iesi seriai No. 506,689 7 Claims. (Cl. 261-434) This invention pertainsto carburetors and more particularly has reference to the-control of acceleration pumps'therefor in accordance with the temperature of the carburetor.

The desirability of regulating the acceleration charge of a carburetorin accordance withthe temperature of the carburetor has long been recognized in the art and various schemes have been proposed forthis purpose; These have generally taken the form of thermally responsive devices for limiting the stroke of the pump associated with the mechanical hookup between the throttle and pump, or temperature responsive valves for relieving pressure upon the accelerat ing charge, or by-passing a portion of the charge back to the float chamber in those types of accelerationpumps-that are actuated by vacuum.

So far asters aware", no one has yet devised a system of temperature "control for vacuum actu- --ated acceleration pumps b y vaiying the vacuum in accordance with the temperature of the carburetor.

An object o f;this invention is to devise a carburetor in which' 'the acceleration pump is actuated' by a vacuum regulated in accordance with the temperature of the carburetor.

Another object of this invention is to provide a carburetor-in which the'acceleration pump operated by a temperature responsive vacuum -which is-at'a-maximum when the carburetor is at its lowest working temperature and at a minimum when the carburetor'is at its highest working temperature.

Still another object of my invention is to de- -vise a vacuum operated acceleration pump in which the stroke of the pump is regulated by varying the vacuum in accordance with the temperature of the carburetor.

With these-and other objects in view which may be incident to my improvements, my invention consists in the combination and arrangement of elements hereinafter described and illustrated in the=accompanying drawing in which:

Figure 1 shows incentral longitudinal section a carburetor embodying my improvements, and

Figure 2 is a fragmentary sectional view, on an enlarged scale, of the" temperature responsive vacuum regulating valve.

In Figure l, the reference numeral 1 indicates the body of a conventional carburetor comprising the usual air intake 2, mixing chamber 3, and mixture outlet 4 controlled by a throttle valve 5. The main nozzle 6 and idle feed '7 communicate through passageways 9 and 10 and port 11 with a 56"*float chamber 12, which is supplied with liquid fuel through inlet 13 from themain fuel tank' (not s'hownlj" Float l4 and valve 15 maintain the liquid fuel at a constant level-indicated by the line X--X in the wellknown mannen'while'a valve 16 seating inport- 11 controls the main flow ofliquid fuel to nozzle 6 and' idle ports 7-. The float chamber 12 is closed by a cover 1'7 to which is integrally attached a cylinder 18 which extends partly into the float chamber 12 and partly above the cover 17 as clearly shown iri- Figure 1. top of cylinder'18' abuts against aprojection 19 carried by the bodyl of the carburetor adjacent the mixture outlet 4, and communicates with the mixture outlet 4 and mixing chamber 3 (when throttle 5 is open) by means of a passageway 20 and port 21.

Slidably"'mounted in cylinder 18 is a doublehollow cylindrical piston '22, theupp'er end of whichcontains a helical spring 23 which tends to thrust the piston down in'opposition to the suction transmitted-from the mixing-chamber 3 and mixture outlet 4 through passageway 20. The lowerend of'the piston 22 is in the'form of 'a'cu'p 24am; contains asmaller piston-'25 adapted for reciprocation therein. Depending-from piston 25 is a hollow stem 26 provided at its lower end with a port 27 and an enlarged head=28 which latter forms a valve controlling aport 29 which establishes communication between the float -chamber 12 and passageway 9"to"nozzle 61 Within the stem 26 is a passageway 30,- which, with-port 27, es-i tablishes communication between float chamber l2 and the interior of cup-24.- A lug- 31 on the upper face of piston 25 prevents the top of cup 24 from closing -theendof passage-way 30 when piston 22 isat the bottom of it's 'stroke. A helical spring 32 surrounds stem 26' and 'bears against the under side of piston 12s,?t-husreturning it tothe top of its stroke after pistori22 returns to'its' uppermost position. a

Communicating with passageway 20 is a lateral bore 33 which leads tothe outsideof the carburetor and is'threaded for thereceptionofascrew plug 34 and a valve seat-35yas shown in Figure :2. Plug 34'is provided with a'central bore 36 which, with an aligned bore37 in 'valveseat 35',-forms'- a communication from thepassageway 20 to the outside atmosphere through a port 37 in a screw cap 38 which is adapted to engage over the end of plug 34.

Slidably mounted in bore 36 and adapted to engage seat 35 is a valve 39, which allows sufiicient clearance in bore 36 to form a free passageway therethrough. The lower end of valve 39 is tapered to fit into and close passage 37 in seat The a when valve 39 is in its lowermost position. The upper end of valve 39 is threaded to engage a plurality of adjusting nuts to and 41 which embrace the free end of a thermally responsive element 42, which is fixed to the upper face of plug 34 as with a screw i3. Thermostat i2 is provided With a hole 44 which registers with bore 36 in plug 34 and through which valve 39 passes with sufficient clearance to provide a free passageway from bore 36 to the space enclosed by cap 38.

The thermostat 42 is so arranged and calibrated as to raise or lower valve 39 a predetermined amount for each degree change in temperature so that the amount of air drawn through vent 3'7 into passageway 20, to reduce the vacuum therein, is regulated in accordance with temperature by the valve 39.

The operation of my carburetor is as follows: When the vacuum or suction in mixture outlet 4 is high and valve 39 is closed, the vacuum acting on piston 22 is aprpoxiznately equally high and is suflicient to hold piston 22 in its uppermost position as shown in Figure 1. This condition of high vacuum in mixture outlet 4 occurs when the throttle 5 is closed (engine idling) and also when the throttle 5 is substantially full open and the engine running at high speed. On the other hand, a condition of low vacuum exists in mixture outlet l when throttle 5 is suddenly opened (as when accelerating) and when the throttle is wide open and the engine is running slow under heavy load, and under conditions of low vacuum in mixture outlet 4, the vacuum acting on piston 22 is too weak to hold it in its uppermost position and spring 23 causes it to descend. If piston 22 descends rapidly (as when the throttle 5 is quickly opened) it applies pressure to the liquid fuel in cup 24 and forces piston 25 down, thus opening port 29. Thereupon a liquid fuel accelerating charge is discharged from cup 24 and also from float chamber 12 to nozzle 6. If the piston 22 descends slowly, as when throttle 5 is opened slowly, it applies pressure to the liquid fuel in cup 24 so gently that said fuel escapes therefrom past piston 25 back into float chamber 12 without moving piston 12, so that no liquid fuel is discharged from cup 24 or chamber 12 through port 29.

The foregoing operations have been considered on the basis of valve 39 being closed which is the case only when the carburetor is at its lowest operating temperature and the maximum accelerating charge is desired. If new valve 39 is partly opened, it permits atmospheric air to be drawn into passage 20, and at once reduces the vacuum in cylinder 18 below the vacuum in mixture outlet 4 and the further valve 39 opens, as with increase in temperature, the further the vacuum in chamber 18 is reduced until a point is reached (with valve 39 fully open) where this vacuum is insufiicient to retract piston 22 against the force of spring 23. In this case the piston 22 remains at the bottom of its stroke regardless of the position of throttle 5 or the fluctuations in vacuum in mixing chamber 4 and no accelerating charge is delivered when the throttle 5 is suddenly opened. With valve 39 partially open, the vacuum in chamber 18 is only partially reduced and the output of the acceleration pump is only correspondingly reduced. In this way the amount of accelerating charge is automatically proportioned to the temperature of the carburetor after the thermostat 42 is once correctly calibrated and set.

While I have shown and described the preferred form of my invention, I desire it to be understood that I do not limit myself to the constructional details disclosed by way of illustration, as it is apparent that these may be changed and modified by those skilled in the art Without departing from the spirit of my invention or exceeding the scope of the appended claims.

I claim:

1. In a carburetor having a mixing chamber, a vacuum operated acceleration pump, a passageway connecting said chamber and pump, and a thermal responsive air bleed for supplying air directly to said passageway, whereby said pump is rendered inoperative at the highest operating temperatures of said carburetor.

2. In a carburetor, a vacuum actuated acceleration pump comprising a cylinder adapted to hold fuel and means separate from said cylinder for modifying said vacuum so that the output of said pump is inversely proportioned to the temperature of the caruretor.

3. In a carburetor, a vacuum operated acce1- eration pump comprising a cylinder adapted to hold fuel and means separate from said cylinder for gradually reducing said vacuum as the temperature of the carburetor increases, whereby the output of said pump is a maximum at the lowest operating temperature of the carburetor and gradually reduced to a minimum at the highest operating temperature of the carburetor.

4. In a carburetor, a vacuum actuated acceleration pump comprising a cylinder adapted to hold fuel and thermal responsive means separate from said cylinder for modifying said vacuum so that the output of said pump is inversely proportioned to the temperature of the carburetor.

5. In a carburetor having a mixing chamber, an acceleration pump comprising ,a cylinder adapted to hold fuel and means separate from said cylinder comprising a chamber subject to the fluctuations of vacuum in said mixing chamoer and a thermal responsive air valve for modifying said vacuum in accordance with the temperature of the carburetor.

6. In a carburetor having a mixing chamber, an acceleration pump comprising a cylinder adapted to hold fuel and a thermostatic needle valve separate from said cylinder for bleeding air into said mixing chamber and modifying the suction actuating said pump in accordance with the temperature of the carburetor.

7. In a carburetor having a mixing chamber, an acceleration pump operated by the vacuum in said chamber comprising a cylinder adapted to hold fuel and a thermostatic air valve separate from said cylinder for modifying said vacuum and controlling the output of said pump in accordance with the temperature of said carburetor.

AUGUSTIN M. PRENTISS. 

